Method for in-situ observation and control of interface flipping during crystal growth by Czochralski method

Abstract

The present invention relates to the field of crystal growth, and discloses a method for in-situ observation and control of interface flipping during the process of growing crystals by the Czochralski method, which is used to diagnose the state of the growth interface in the Czochralski method crystal growth system, and includes the following specific steps: during the crystal growth process, real-time acquisition of the interface electromotive force U between the crystal and the melt in the Czochralski method crystal growth system; synchronous recording of the movement trajectory of the interface electromotive force U over time, if a sudden reverse change is observed in the movement trajectory of U over time, it is judged that the grown crystal is about to undergo interface flipping, thereby realizing in-situ observation of interface flipping. The present invention solves the problem that the prior art is difficult to adapt to complex crystal growth environments and has demanding conditions, and has the characteristics of being able to save manpower and material costs, and being able to guide time-varying temperature fields and convection fields.

Description

Technical Field

[0001] The present invention relates to the field of crystal growth, and more specifically to a method for in-situ observation and regulation of interface flipping during crystal growth by a Czochralski method. Background Art

[0002] The Czochralski method has the advantages of producing crystals of large size and high quality. It is widely used in more than 90% of crystal growth equipment worldwide. It can mass-produce materials such as lithium niobate (LN), single crystal silicon, and yttrium aluminum garnet (YAG), providing unparalleled support for applications in optics, lasers, semiconductors, and electronic devices. Although the Czochralski method is extremely widely used in crystal growth and has formed a set of mature theories, the in-situ visualization of the shape and evolution of the growth interface during the Czochralski method crystal growth process has always troubled crystal growth practitioners. Because this is a hidden area, it is almost impossible to observe the state of the growth interface in situ during the growth process. However, in the process of crystal growth by the Czochralski method, the shape of the growth interface has a crucial influence on the quality of the crystal. For example Figure 8 As shown in the figure, the shape of the crystal growth interface can be generally divided into three types on a macroscopic scale: flat, concave, and convex. When growing with a convex interface, the crystal is not easy to detach from the interface and the growth is easy to control, but this growth method will make it difficult to expel the crystal inclusions, which may cause defects such as cellular growth, large stress, and dislocations. Once the crystal diameter is too large, it may even crack. In contrast, crystals grown with a concave interface have low stress and do not contain inclusions. However, under this growth method, the contact between the crystal and the melt is unstable, the growth is difficult to control, and it is easy to melt back or even fall off. In most crystal growth processes, crystals grown with a flat interface have low stress and are ideal interfaces for crystal growth.

[0003] The specific interface shape to be selected for growing crystals needs to be determined in combination with the characteristics of the crystal and its melt itself and the needs of practical applications. However, no matter which growth interface shape is selected, the interface shape should be kept unchanged during the crystal growth process. However, due to the complex convection and growth environment, it is difficult for the interface shape to remain unchanged. Taking oxide crystals as an example, the growth interface often undergoes a transition from convex to concave, that is, the interface flipping phenomenon. It is generally believed that the direct cause of interface flipping is the change in dominant convection, that is, the exchange of advantages between forced convection and natural convection. Forced convection is a hot plume driven by rotation that flows outward from the bottom and meridian of the crucible; natural convection is a cold plume driven by buoyancy and surface tension that flows inward from the edge of the crucible to the growth interface. When natural convection dominates, the growth interface is a convex interface; when forced convection dominates, the growth interface is a flat or concave interface. Generally speaking, in the early stage of crystal pulling growth, the liquid level is high, the melt temperature difference is large, and the natural convection effect is strong; and during this period, the crystal diameter is small and the forced convection effect is weak. Therefore, in the early stage of growth, natural convection dominates and the growth interface is a convex interface. As the crystal grows, the liquid level drops, the temperature difference of the melt decreases, and the intensity of natural convection decreases; at the same time, the crystal diameter increases, and the forced convection also increases, so forced convection begins to dominate, and the interface shape will flip to a concave interface. Interface flipping usually changes the morphology and structure of the growing crystal, introducing a large number of defects such as dislocations and vacancies inside the crystal, and then the performance, reliability and degradation behavior of the crystal device will be adversely affected. Therefore, in situ observation and analysis of interface flipping is crucial to optimize growth parameters and ensure a controllable and reproducible crystal growth process.

[0004] Unfortunately, the current means of assisting the growth of crystals by the Czochralski method, such as controlling the crucible temperature (thermocouple) and image recognition, have achieved crystal contour control, but none of them can in-situ feedback the state of the growth interface in a crystal growth environment with high temperature, high pressure, coexistence of solid, liquid and gas phases, and strong electromagnetic interference. In addition, the widely used load sensors are affected by the load range and resolution, and can hardly detect small weight changes, such as interface flipping and the formation of growth stripes. Under specially designed experimental conditions and detection environments, the observation of interface evolution can be achieved through synchrotron radiation x-rays, energy-solved neutron scattering, ultrasound and other technologies, but these technologies have almost harsh experimental conditions, and the difficulty and cost of implementation are too high. The guiding significance for time-varying temperature fields and convection fields is also very limited. In addition, the application of these technologies requires extremely high literacy of operators, and there are also strict restrictions on the materials and structures of crucibles and heating elements; and most of these methods have radiation risks, requiring professional equipment and radiation safety measures to avoid harm to operators and the environment, so it is difficult to apply them in industrial production. Methods such as optical imaging and electron beam technology that are being promoted can observe the growth interface in real time to a certain extent. However, these methods are limited by crystal transparency, surface reflection and imaging resolution, and their adaptability to different types of crystals is not uniform, making it difficult to achieve ideal results.

[0005] In order to avoid the impact of unstable fluctuations of the growth interface on the quality of the crystal, crystal growth researchers have developed a variety of technologies to suppress interface fluctuations, including variable speed rotation of crystals or crucibles (ACRT), loading magnetic fields, ultrasonic fields, gravity fields, and other technologies to control convection to suppress interface fluctuations. However, the premise for the effective use of this type of interface fluctuation suppression technology is to be able to detect the interface state in situ, rather than relying more on empirical methods, that is, to explore the interface regulation laws by observing a large number of crystal growth processes, which consumes a lot of time and labor costs that are difficult to estimate. Obviously, for the complex and sensitive growth interface, a hidden area, due to the lack of in-situ feedback technology for the growth interface state, it is difficult for researchers to observe and regulate the interface flipping in real time throughout the crystal growth cycle. Therefore, in view of the actual needs of production and the limitations of existing technologies, the crystal industry urgently needs a means to observe and regulate the interface flipping in situ during crystal growth. Related studies have shown that the interface electromotive force U method has significant advantages, which can make up for the shortcomings of traditional measurement methods and display the state and evolution of the growth interface in situ. The interface phase electromotive force U is an inherent electromotive force existing between the growing crystal and the melt. It is the crystallization electromotive force ( ) and the thermoelectric potential between the solid and liquid phases ( ), and the thermoelectric potential is composed of the supercooling potential ( ) and the Seebeck electromotive force between the crystal and the melt ( ) is composed as shown in formula (1-2):

[0006] (1)

[0007] (2)

[0008] In summary, in view of the problems that existing observation and control technologies are difficult to adapt to complex crystal growth environments and have stringent conditions, how to invent a method that can relatively simply achieve in-situ observation and control of interface flipping during the Czochralski crystal growth process is a technical problem that urgently needs to be solved in the field of crystal growth technology. Summary of the invention

[0009] In order to solve the problem that the prior art is difficult to adapt to complex crystal growth environments and has stringent conditions, the present invention provides a method for in-situ observation and regulation of interface flipping during the crystal growth process by the Czochralski method, which has the characteristics of saving manpower and material costs and guiding time-varying temperature and convection fields.

[0010] In order to achieve the above-mentioned purpose of the present invention, the technical scheme adopted is as follows:

[0011] The method for in-situ observation of interface flipping during the Czochralski method crystal growth process is used to diagnose the state of the growth interface in the Czochralski method crystal growth system, and includes the following specific steps:

[0012] During the crystal growth process, the interface electromotive force U between the crystal and the melt in the Czochralski crystal growth system is collected in real time;

[0013] The movement trajectory of the interface electromotive force U with time is recorded synchronously. If a sudden reverse change is observed in the movement trajectory of U with time, it is judged that the interface of the grown crystal will flip.

[0014] Preferably, the interface electromotive force U between the crystal and the melt is collected. The specific method is: the two poles of the voltmeter are electrically connected to the seed crystal and the bottom of the crucible respectively, and the interface electromotive force U is collected.

[0015] Furthermore, the interface electromotive force U between the crystal and the melt was collected at a sampling rate of 10 Hz, and the collected U was filtered to eliminate the interference of the DC component.

[0016] Furthermore, the movement trajectory of the interface electromotive force U over time is synchronously recorded, specifically: the changing trend of the interface electromotive force U over time T is recorded; during the crystal growth process, when no interface reversal occurs, the absolute value of U shows an increasing trend over time. If the absolute value of U is observed to suddenly show a decreasing trend over time, it is judged that the grown crystal will undergo an interface reversal from convex to concave or from flat to concave.

[0017] Furthermore, if a quadratic trend change is observed in which the absolute value of U in the UT curve decreases over time and then increases, it is judged that the interface flip from convex to concave or from flat to concave has been completed.

[0018] Furthermore, after determining that the interface flip from convex to concave or from flat to concave has been completed, further data analysis is performed on the secondary trend change of the UT curve when the interface flip occurs, and the heat flow change during the interface flip process and the crystal growth interface state before and after the interface flip occurs are obtained.

[0019] Furthermore, whether the interface flipping occurs is evaluated by observing the diameter of the grown crystal, and the specific steps are as follows:

[0020] When the seed crystal is placed, the radial temperature difference between the center temperature and the edge temperature of the growth interface in the Czochralski crystal growth system is collected. ;

[0021] Based on the measured radial temperature difference The critical crystal diameter for interface flipping under the current Czochralski crystal growth system is calculated. ;

[0022] During the crystal growth process, the diameter of the growing crystal is observed in real time;

[0023] If the critical crystal diameter is observed If the difference between the diameter of the growing crystal and the diameter of the growing crystal is less than a preset threshold, it is determined that interface flipping will occur during the crystal growth process.

[0024] Furthermore, the radial temperature difference between the center temperature and the edge temperature of the growth interface in the Czochralski crystal growth system is collected. , the specific steps are:

[0025] When the crystal is placed, the first thermocouple is inserted into the melt along with the seed crystal; the first thermocouple is ensured to be in close contact with the seed crystal and located at the center of the growth interface; the second thermocouple is set at the edge of the crucible on the same horizontal line;

[0026] Connect the thermometer to the first thermocouple and the second thermocouple to collect the center temperature of the growth interface in the Czochralski crystal growth system. and the temperature of the crucible edge at the same level as the growth interface ;

[0027] Will minus the temperature The radial temperature difference in the growth environment is obtained by .

[0028] Furthermore, based on the measured radial temperature difference The critical crystal diameter for interface flipping under the current Czochralski crystal growth system is calculated. , the specific formula is:

[0029]

[0030] in, is the acceleration due to gravity, is the crucible radius, is the rotation speed of the crystal, is the volume expansion coefficient of the grown crystal.

[0031] The method for in-situ regulating interface flipping during the Czochralski method crystal growth process comprises the following specific steps:

[0032] When the crystal is about to or is undergoing interface flipping:

[0033] Determine whether it is necessary to avoid or reduce the effect of interface flipping on crystal growth; if so, control the interface flipping by reducing the rotation speed or increasing the radial temperature gradient, or by one or more methods;

[0034] Determine whether it is necessary to accelerate the process of interface flipping or enhance the effect of interface flipping on crystal growth, and if so, control the interface flipping by increasing the rotation speed or reducing the radial temperature gradient, or one or more methods;

[0035] Otherwise no regulation.

[0036] The beneficial effects of the present invention are as follows:

[0037] The present invention collects the interface electromotive force U between the crystal and the melt in the Czochralski crystal growth system in real time during the crystal growth process, and monitors in real time whether the interface flip occurs during the crystal growth process by observing the trend change of the electromotive force U, so as to take corresponding preventive and control measures, thereby avoiding or reducing the influence of the interface flip on the crystal growth, and obtaining a higher quality crystal. The present invention also provides a method for adjusting the critical flip diameter before the growth process and how to avoid and control the interface flip during the growth process by theoretically calculating the critical crystal diameter of the interface flip. Through this method and device, the occurrence time of the interface flip can be predicted in real time, and real-time guidance can be provided for the optimization of the growth parameters, so as to adjust the growth conditions before causing adverse effects on the growth, and maximize the quality of crystal growth. The interface flip can also be reasonably utilized and regulated to provide theoretical guidance for designing crystals with specific properties. In summary, the present invention solves the problem that the prior art is difficult to adapt to the crystal growth environment and the conditions are demanding, and has the characteristics of saving manpower and material costs, and can guide the time-varying temperature and convection field. It is a powerful guarantee for the development of large-size high-quality crystals with controllable defects, and will provide reliable interface state information for the growth of oxides, semiconductors and metal crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic flow chart of a method for in-situ observation of interface flipping during crystal growth by the Czochralski method of the present invention.

[0039] Figure 2 This is a schematic diagram of the Czochralski crystal growth system.

[0040] Figure 3 It is a schematic diagram of the connection method of the Czochralski crystal growth system.

[0041] Figure 4 It is a schematic flow chart of the method for in-situ observation of interface flipping during the crystal growth process by the Czochralski method of the present invention in Example 2.

[0042] Figure 5 This is a UT curve diagram in Example 3.

[0043] Figure 6 This is a distribution diagram of the growth interface shape under the ultraviolet light background in Example 3.

[0044] Figure 7 This is a schematic diagram of the corresponding dimensions of the crystal at the interface flip point in Example 3.

[0045] Figure 8 This is a schematic diagram of the shapes of different growth interfaces during the Czochralski method of crystal growth.

[0046] In the figure, 1 is a voltmeter, 2 is a melt, 3 is a crystal, 4 is a rotating device, 5 is a crystal rotating rod, 6 is a seed crystal rod, 7 is a seed crystal, 8 is a crucible, 9 is a heat-insulating cover, 10 is a heat-insulating material, 11 is a heating coil, 12 is a temperature meter, 13 is the first thermocouple, and 14 is the second thermocouple. DETAILED DESCRIPTION

[0047] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] Example 1

[0049] like Figure 1 As shown, the method for in-situ observation of interface flipping during the Czochralski method crystal growth process is used to diagnose the state of the growth interface in the Czochralski method crystal growth system, and includes the following specific steps:

[0050] During the growth of crystal 3, the interface electromotive force U between crystal 3 and melt 2 in the Czochralski crystal growth system is collected in real time;

[0051] The movement trajectory of the interface electromotive force U with time is recorded synchronously. If a sudden reverse change is observed in the movement trajectory of U with time, it is determined that the interface of the grown crystal 3 is about to flip.

[0052] In this embodiment, the Czochralski crystal growth system is as follows: Figure 2 As shown, the Czochralski crystal growth system includes a crystal device and a melt device; the crystal device includes a rotating device 4, a crystal rotating rod 5, and a seed crystal rod 6; the melt device includes a crucible 8; the rotating device 4 is rotatably connected to one end of the crystal rotating rod 5, and is used to drive the crystal rotating rod 5 to rotate; the other end of the crystal rotating rod 5 is fixedly connected to one end of the seed crystal rod 6; the other end of the seed crystal rod 6 is fixedly connected to one end of the seed crystal 7; the raw material is arranged in the crucible 8; when the Czochralski crystal growth system is used to grow crystals, the raw material is heated to melt 2, the other end of the seed crystal 7 is inserted into the melt 2, the crystal rotating rod 5 rotates at a set speed, and a set temperature change rate is applied to the Czochralski crystal growth system to make the crystal 3 grow.

[0053] The rotating device 4 includes a rotating motor and a conductive slip ring; the Czochralski crystal growth system adopts a reasonable and scientific heating and heat preservation structure to reduce the impact of temperature fluctuations and environmental interference on the experiment. The pulling rod consists of two sections, one section is a crystal rotation rod 5 connected to the rotating motor and the conductive slip ring, and the other section is a precious metal seed crystal rod 6 connected to the seed crystal 7, wherein the conductive slip ring and the crystal rotation rod 5 are fixed by a tripod to reduce the impact of eccentric rotation on the growth of the crystal 3.

[0054] It also includes a heating device, which includes a heat-insulating cover 9, a heat-insulating material 10, and a heating coil 11; the heat-insulating material 10 is arranged in the heat-insulating cover 9; the heating coil 11 is arranged around the heat-insulating cover 9; when heating the raw materials of the Czochralski crystal growth system, the crucible 8 of the Czochralski crystal growth system is placed in the heat-insulating material 10; the raw materials are heated by the heating coil 11 to obtain a melt 2; the heat-insulating cover 9 and the heat-insulating material 10 can ensure that the raw materials in the crucible 8 are fully melted to obtain a melt 2.

[0055] In a specific embodiment, the interface electromotive force U between the crystal 3 and the melt 2 is collected by electrically connecting the two poles of the voltmeter 1 to the seed crystal 7 and the bottom of the crucible 8 respectively, and collecting the interface electromotive force U.

[0056] In this embodiment, the voltmeter 1 uses the precious metal wire as a conductor and an electrode, passes the conductor through the rotating end of the conductive slip ring, connects the positive electrode to the end of the seed crystal 7, and connects the negative electrode to the bottom of the precious metal crucible 8; wherein, the conductor from the fixed end of the conductive slip ring to the voltmeter 1 needs to be insulated. At the same time, the reverse connection method of connecting the positive electrode to the bottom of the crucible 8 and the negative electrode to the end of the seed crystal 7 can also achieve a similar effect.

[0057] In a specific embodiment, the interface electromotive force U between the crystal 3 and the melt 2 is collected at a sampling rate of 10 Hz, and the collected U is filtered to eliminate interference from direct current components.

[0058] In a specific embodiment, the movement trajectory of the interface electromotive force U over time is synchronously recorded, specifically: the change trend of the interface electromotive force U over time T is recorded; during the crystal growth process, when the interface reversal does not occur, the absolute value of U shows an increasing trend over time, if it is observed that the absolute value of U suddenly shows a decreasing trend over time, it is judged that the grown crystal 3 is about to undergo an interface reversal from convex to concave or from flat to concave.

[0059] In this embodiment, after determining that the interface flip from convex to concave or from flat to concave has been completed, further data analysis is performed on the secondary trend change of the UT curve when the interface flip occurs to obtain the heat flow change during the interface flip process and the growth interface state of the crystal 3 before and after the interface flip occurs.

[0060] During the crystal growth process, the diameter of the growing crystal is observed in real time and the interfacial electromotive force U between the crystal and the melt in the Czochralski crystal growth system is collected.

[0061] In a specific embodiment, if a quadratic trend change is observed in which the absolute value of U in the UT curve completely decreases over time and then rises back to the original curve, it is determined that the interface flip from convex to concave or from flat to concave has been completed.

[0062] In this embodiment, in special cases, an interface flip from concave to convex or from concave to flat may occur; if a quadratic trend change is observed in which the absolute value of U in the UT curve suddenly rises significantly more with time and then drops back to the original curve, it is determined that the interface flip from concave to convex or from concave to flat has been completed.

[0063] Example 2

[0064] More specifically, in this embodiment, the connection method of the Czochralski crystal growth system is as follows: Figure 3 shown.

[0065] In a specific embodiment, Figure 4 As shown, whether interface flipping occurs is also evaluated by observing the diameter of the grown crystal 3, and the specific steps are:

[0066] When the seed crystal 7 is placed in the crystal, the temperature of the contact point between the seed crystal and the growth interface in the Czochralski crystal growth system is collected, that is, the radial temperature difference between the center temperature of the growth interface and the edge temperature of the crucible 8 on the same horizontal line ;

[0067] Based on the measured radial temperature difference The critical crystal diameter for interface flipping under the current Czochralski crystal growth system is calculated. ;

[0068] During the growth of the crystal 3, the diameter of the growing crystal 3 is observed in real time;

[0069] If the critical crystal diameter is observed If the difference between the diameter of the growing crystal 3 and the diameter of the growing crystal 3 is less than a preset threshold, it is determined that interface flipping will occur.

[0070] In this embodiment, the threshold is 0.

[0071] In this embodiment, the diameter of the growing crystal 3 is observed in real time by a CCD image monitoring method.

[0072] In a specific embodiment, Figure 3 As shown, the radial temperature difference between the center temperature and the edge temperature of the growth interface in the Czochralski crystal growth system is collected. , the specific steps are:

[0073] When the crystal is lowered, the first thermocouple 13 is inserted into the melt 2 along with the seed crystal 7; it is ensured that the first thermocouple 13 is closely attached to the seed crystal 7 and is located at the center of the growth interface; the second thermocouple 14 is arranged at the edge of the crucible 8 on the same horizontal line;

[0074] The temperature meter 12 is connected to the first thermocouple 13 and the second thermocouple 14 to respectively collect the center temperature of the growth interface in the Czochralski crystal growth system. and the temperature of the edge of the crucible 8 at the same level as the growth interface ;

[0075] Will minus the temperature The radial temperature difference in the growth environment is obtained by .

[0076] In this embodiment, the first thermocouple 13 collection point is located at the end of the seed crystal 7 and is fixed with a precious metal wire, and the second thermocouple 14 collection point is located at the edge of the crucible 8 parallel to the growth interface, thereby achieving the simultaneous recording of the interface electromotive force U and temperature changes during the growth of the crystal 3 without interfering with the normal growth of the crystal 3. The use of a vertically movable thermocouple to measure the temperature at the center of the melt 2 can better stabilize the rotating device axially.

[0077] In this embodiment, the first thermocouple is inserted into the melt along with the seed crystal 7 to measure the temperature of the growth interface at the center of the crucible, and compared with the temperature at the edge of the crucible 8 on the same horizontal line to obtain the radial temperature difference under the growth environment. .

[0078] In a specific embodiment, based on the measured radial temperature difference The critical crystal diameter for interface flipping under the current Czochralski crystal growth system is calculated. , the specific formula is:

[0079]

[0080] in, is the acceleration due to gravity, is the crucible radius, is the rotation speed of the crystal, is the volume expansion coefficient of the grown crystal.

[0081] like Figure 4 As shown, after determining that the interface flipping of the grown crystal 3 will occur, the interface flipping is also regulated based on the determination, and the specific steps are:

[0082] Determine whether it is necessary to avoid or reduce the effect of interface flipping on the growth of the crystal 3; if so, control the interface flipping by reducing the rotation speed or increasing the radial temperature gradient, or by one or more methods;

[0083] It is determined whether it is necessary to accelerate the process of interface flipping or enhance the effect of interface flipping on the growth of crystal 3. If so, the interface flipping is regulated by increasing the rotation speed or reducing the radial temperature gradient by one or more methods.

[0084] Example 3

[0085] In this embodiment, the method for in-situ observation of interface flipping during the Czochralski method crystal growth process disclosed in the present invention is also experimentally verified.

[0086] The experimental Czochralski crystal growth system is as follows Figure 2 As shown, the crucible radius is 50 mm.

[0087] Before the crystal growth experiment, the first thermocouple was inserted into the melt 2 along with the seed crystal 7 to measure the temperature of the growth interface at the center of the crucible 8, and compared with the temperature at the edge of the crucible 8 on the same horizontal line to obtain the growth environment. Then, the crystal growth experiment was started at a pulling speed of 4 mm / h and a crystal rotation speed of 20 r / min, and the interface electromotive force U and seed crystal temperature during the entire crystal growth process were simultaneously recorded. , Crucible edge temperature During the crystal growth process, as the crystal grows, the Seebeck electromotive force increases due to the increase in temperature difference between the crystal and the growth interface and the melt. increases, which in turn causes the Seebeck electromotive force U to increase as well. , is the Seebeck coefficient of the crystal, is the Seebeck coefficient of the melt, are the temperatures of the seed crystal, interface, and melt, respectively, where the interface temperature is generally the melting point. It is worth noting that related studies have shown that when the Czochralski method is used to grow lithium niobate crystals, the Seebeck coefficients of the crystal and melt are , .

[0088] However, as the crystal grows to a certain extent, the interface electromotive force U shows a sudden drop and then an increase, such as Figure 5 As shown in Figure 2, this corresponds to the time period when the interface flip occurs. This is because when the interface flip occurs, the forced convection that carries more heat takes advantage at the interface, causing the melt temperature near the growth interface to The crystal melts back, which reduces the interface electromotive force U. The growth interface is thus flipped from convex to concave. Then, the crystal 3 is cut along the Z direction to obtain a 1 mm thick slice. After polishing, the following is obtained under a purple light background: Figure 6 The interface shape distribution diagram shown in the figure, as shown in the dotted area, can clearly observe the interface flip phenomenon during the crystal growth process. Under the crystal growth condition of 20r / min, It can be obtained that the critical crystal 3 diameter when interface flipping occurs should be 22 mm. At the same time, if Figure 7 As shown in the figure, the actual crystal diameter when the interface flip occurs is 24 mm, and the theoretical prediction is highly consistent with the experimental results, which shows that the present invention can provide valuable guidance for the prevention and regulation of interface flip under a specific temperature field. In addition, combined with the actual growth rate of crystal 3 when the liquid level drops, that is, the total length of crystal 3 divided by the growth time: 4.9 / 10.1=4.85 mm / h, and the length of crystal 3 of 15 mm when the interface flip occurs, it can be obtained that the growth time when the interface flip occurs is 3.09 h (11134 s), as shown in the figure. Figure 6 As shown in the enlarged inset in Figure 2, this is consistent with the time when the bulge appears in the UT curve measurement, which is 3.14h (11306s).

[0089] The small error between the two is mainly because the calculated crystal growth rate is actually the average growth rate of the entire growth process, and at each different growth stage, the actual growth rate of the crystal will have a certain deviation from the average growth rate. Despite this, the in-situ observation results of the UT curve are still in good agreement with the actual measurement results, which fully demonstrates the sensitivity and accuracy of the in-situ observation of interface flipping of the present invention. The high consistency of the experimental results, theoretical calculation results, and UT curve observation results also shows that the in-situ observation and regulation of interface flipping of the present invention has extremely strong application value.

[0090] Example 4

[0091] The method for in-situ regulating interface flipping during the Czochralski method crystal growth process comprises the following specific steps:

[0092] When crystal 3 is about to or is experiencing interface flipping:

[0093] Determine whether it is necessary to avoid or reduce the effect of interface flipping on the growth of the crystal 3; if so, control the interface flipping by reducing the rotation speed or increasing the radial temperature gradient, or by one or more methods;

[0094] Determine whether it is necessary to accelerate the process of interface flipping or enhance the effect of interface flipping on the growth of crystal 3, and if so, control the interface flipping by increasing the rotation speed or reducing the radial temperature gradient, or one or more methods;

[0095] Otherwise no regulation.

[0096] In this embodiment, the two methods of observing and regulating interface flipping are combined to achieve prediction of interface flipping, real-time observation and confirmation of flipping completion, so as to achieve more comprehensive real-time and post-event adjustments later.

[0097] The present invention realizes in-situ observation and regulation of interface flipping by theoretically calculating the critical flipping diameter and real-time monitoring of the interface electromotive force change during the growth process of the crystal 3, and also provides a method for adjusting the critical flipping diameter before the growth process and how to avoid and regulate the interface flipping during the growth process. Through this method, the occurrence time of the interface flipping can be predicted in real time, which is convenient for taking corresponding preventive and regulatory measures to obtain a higher quality crystal 3. In summary, the ability of the present method to diagnose interface flipping in situ greatly makes up for the shortcomings of the existing crystal 3 growth sensor, and can accurately observe and regulate the interface flipping phenomenon during the growth process of the crystal 3 in real time. This method of in-situ observation and regulation of interface flipping can provide real-time feedback of the crystal instability growth regulation method such as interface flipping, and provide real-time guidance for the optimization of growth parameters, so as to adjust the growth conditions before causing adverse effects on the growth, and maximize the quality of crystal growth. This will provide extremely valuable guidance for the growth of large-size, high-quality crystals 3.

[0098] Obviously, the above embodiments of the present invention are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for in-situ observation of interface flipping during the Czochralski method crystal growth process, used to diagnose the state of the growth interface in the Czochralski method crystal growth system, characterized by: The specific steps include: During the growth of the crystal (3), the interface electromotive force U between the crystal (3) and the melt (2) in the Czochralski crystal growth system is collected in real time; The time trajectory of the interface electromotive force U is recorded synchronously. If a sudden reverse change is observed in the time trajectory of U, it is judged that the interface of the grown crystal (3) is about to flip.

2. The method for in-situ observation of interface flipping during crystal growth by the Czochralski method according to claim 1, characterized in that: The interface electromotive force U between the crystal (3) and the melt (2) is collected. The specific method is: the two poles of the voltmeter (1) are electrically connected to the seed crystal (7) and the crucible (8) respectively, and the interface electromotive force U is collected.

3. The method for in-situ observation of interface flipping during crystal growth by the Czochralski method according to claim 2, characterized in that: The interface electromotive force U between the crystal (3) and the melt (2) is collected at a sampling rate of 10 Hz, and the collected U is filtered to eliminate the interference of the DC component.

4. The method for in-situ observation of interface flipping during crystal growth by the Czochralski method according to claim 1, characterized in that: The movement trajectory of the interface electromotive force U with time is recorded synchronously, specifically: the change trend of the interface electromotive force U with time T is recorded; during the crystal growth process, when the interface flipping does not occur, the absolute value of U shows an increasing trend with time. If the absolute value of U is observed to suddenly show a decreasing trend with time, it is judged that the grown crystal (3) is about to undergo an interface flip from convex to concave or from flat to concave.

5. The method for in-situ observation of interface flipping during crystal growth by the Czochralski method according to claim 4, characterized in that: If the absolute value of U in the UT curve is observed to show a quadratic trend change of decreasing over time and then increasing, it is judged that the interface reversal from convex to concave or from flat to concave has been completed.

6. The method for in-situ observation of interface flipping during crystal growth by the Czochralski method according to claim 5, characterized in that: After judging that the interface flip from convex to concave or from flat to concave has been completed, further data analysis is performed on the secondary trend change of the UT curve when the interface flip occurs, and the heat flow change during the interface flip process and the crystal (3) growth interface state before and after the interface flip occurs are obtained; if the absolute value of U in the UT curve is observed to show a complete secondary trend change of decreasing with time and then rising back to the original curve, it is judged that the interface flip from convex to concave or from flat to concave has been completed; In special cases, an interface reversal from concave to convex or from concave to flat may also occur; if the absolute value of U in the UT curve is observed to rise suddenly and significantly with time and then fall back to the original curve, it can be judged that the interface reversal from concave to convex or from concave to flat has been completed.

7. The method for in-situ observation of interface flipping during crystal growth by the Czochralski method according to claim 1, characterized in that: Whether interface inversion occurs is also evaluated by observing the diameter of the grown crystal (3), and the specific steps are as follows: When the seed crystal (7) is placed, the radial temperature difference between the center temperature and the edge temperature of the growth interface in the Czochralski crystal growth system is collected. ; Based on the measured radial temperature difference The critical crystal (3) diameter for interface flipping in the current Czochralski crystal growth system is calculated. , the specific formula is: in, is the acceleration due to gravity, is the crucible radius, is the rotation speed of the crystal, is the volume expansion coefficient of the grown crystal; During the growth of the crystal (3), the diameter of the growing crystal (3) is observed in real time; If the critical crystal (3) diameter is observed If the difference between the diameter of the growing crystal (3) and the diameter of the growing crystal (3) is less than a preset threshold, it is determined that interface flipping will occur during the growth process of the crystal (3).

8. The method for in-situ observation of interface flipping during crystal growth by the Czochralski method according to claim 7, characterized in that: Collecting the radial temperature difference between the center and edge temperatures of the growth interface in a Czochralski crystal growth system , the specific steps are: When the crystal is lowered, the first thermocouple (13) is inserted into the melt (2) along with the seed crystal (7); ensuring that the first thermocouple (13) and the seed crystal (7) are tightly fitted and located at the center of the growth interface; and the second thermocouple (14) is arranged at the edge of the crucible (8) on the same horizontal line; The temperature meter (12) is connected to the first thermocouple (13) and the second thermocouple (14) to respectively collect the center temperature of the growth interface in the Czochralski crystal growth system. and the temperature of the edge of the crucible (8) at the same level as the growth interface ; Will minus the temperature The radial temperature difference in the growth environment is obtained by .

9. A method for in-situ control of interface flipping during the Czochralski method of growing crystals, characterized in that: The method for in-situ observation of interface flipping during the Czochralski method crystal growth process according to any one of claims 1 to 8 comprises the following specific steps: When the crystal (3) is about to or is undergoing interface flipping: Determine whether it is necessary to avoid or reduce the effect of interface flipping on the growth of the crystal (3); if so, control the interface flipping by reducing the rotation speed or increasing the radial temperature gradient, or by one or more methods; Determine whether it is necessary to accelerate the process of interface flipping or enhance the effect of interface flipping on the growth of crystal (3); if so, control the interface flipping by increasing the rotation speed or reducing the radial temperature gradient, or by one or more methods; Otherwise no regulation.

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